When utility vehicles, having a rigid frame extending from the cab through the bed, are loaded with cargo exceeding the weight specifications of the vehicles suspension system, the rear of the vehicle experiences a downward movement while the front of the vehicle correspondingly rises. This shift of the suspension system toward its outer extremes defeats its purpose of providing a smooth and stable ride. This shifting action causes a vehicle to become unstable as there is little strength remaining to the leaf suspension system to safely support the vehicle as it moves across uneven surfaces.
To compensate for this problem, some vehicle owners elect to order costly heavy-duty suspension systems while others choose to equip their vehicle with overload spring systems. The relative cost of both these remedies is great, as they are only necessary during heavy load bearing conditions exceeding the outer limitations of the standard suspension system working parameters.
U.S. Pat. No. 3,069,149 discloses a form of auxiliary overload structure including a pair of rubber bumpers which make contact upon the over compression of the suspension coil springs under heavy load conditions. Upon contact between the bumpers, the rear of the vehicle is prevented from shifting further downward. Although this disclosure effectively provides for a more level vehicle under heavy load conditions, when the rubber bumpers are in contact and the vehicle hits a bump, there is little spring action within the rubber bumpers to provide for shock absorption.
U.S. Pat. No. 3,850,444 to Wright discloses an alternative overload spring arrangement. This invention provides for the addition of an extra spring member designed to work in conjunction with the standard equipment so as to emulate a suspension system designed with heavier coil springs. While effectively providing for vehicle stability and shock adsorption, this disclosure fails to modify the behavior of the leaf springs provided as standard equipment.
U.S. Pat. No. 4,671,535, by the present inventor, describes an abutment structure attached to a vehicle frame which comes into direct contact with a vehicle's leaf springs. This system effectively provides for a forward shift of the suspension system's fulcrum upon contact between the leaf spring and the abutment structure. Although the device effectively modifies the behavior of the standard suspension system and increases its load carrying capability, it is relatively expensive and difficult to install. Accordingly, there remains a need for an inexpensive apparatus which provides shock absorption and effectively increases the load bearing capabilities of standard vehicular suspension systems.